How does that work? Kneedragging

In my multiple posts on my trip to Indianapolis for the MotoGP race, I’ve gotten several questions about how the riders can lean over that far and not hurt themselves.  The answers, my friends, are knee pucks.

Through the 1960s or so, racers rode motorcycles just the way you might naturally ride…in more or less the same position all the time, knees against the tank.  This keeps the motorcycle and rider more or less in a straight line, with the center of gravity more or less stationary.  This is all well and good until you’re leaning the motorcycle over…there’s only so much ground clearance to be had.

Eventually, motorcycle racers began to experiment with moving their body off of the seat to lower the center of gravity in the turns.  This way the motorcycle uses less overall lean angle (and so doesn’t scrape hard parts) but the center of gravity of the bike/rider system is shifted to the inside of the turn, tightening the turning radius.

Through the 60s, this new style began to develop, led by racing legends like Mike Hailwood and Barry Sheene, in which the inside knee was opened away from the tank.  The next step was moving the butt off of the seat, which was raised to a new art by “King” Kenny Roberts, the American former dirt-track racer who dominated motorcycle roadracing in the late 1970’s.  Roberts was allegedly the first racer to actually drag his knees on the asphault, and to prevent his leathers from getting holes worn in them, he started wrapping them in tape.  And depending upon who you listen to, he actually taped beer can bottoms to his knees after a while.

In modern motorcycle racing (and hard street riding) it’s customary to have hard plastic pucks attached just below the knees via Velcro patches so that the pucks can be replaced when they are worn out, like these guys here (not mine!):

This way, when the knee touches down, the plastic is gradually worn away but doesn’t suddenly grab the tarmac and pull the knee.

I’m told that racers just use the knee as sort of a gauge to show how far over they’re leaning at any given moment, although supposedly if the bike just barely starts to slide it’s possible to “save it on the knee” by applying pressure through the knee to the ground to pick it back up just a little bit.  I sure as hell wouldn’t know!

My leathers had knee sliders, but the only contact they made with the asphault was when the rest of my ass was on the asphault, too.  😦

Any questions?

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4 Responses

  1. The last line made me laugh! I hope you’ve never had a fall like that though…my partner got hit by a car on his bike about 6 or 7 years ago, and luckily only broke his foot. His brother has had three major accidents, the last of which involved major skin grafts and four months in hospital. He hasn’t been able to afford to replace his bike since then, but still yearns after it. I’ve only been on Ian’s bike (which is only a 125) a few times but can totally understand why, despite the risks, it is so addictive! I could barely get the grin off my face for weeks!

    Yes, actually, I’ve had two low-speed accidents – one when a car ran me off the road, and one when the rear wheel slid out (hadn’t broken in the tires enough to be leaning as hard as I was that day, sadly). In the first case, I went into a ditch and sprained both wrists, in the latter I slid into a guard rail but was okay except for a bruise on my back. That’s why leather is your friend.

    That last line in your comment is exactly why I ride.

  2. This helps bring “us” into “your” world. I am thinking a lesson on tires being able to grip at that angle might be nice too.

    I can’t image you can’t be “in the gas” in that extreme position…can you?

    Yes, to a degree. The more you accelerate the more the bike is going to want to either stand up or slide out, but that’s really no different than a car sliding out of a turn if you think about it. The theory is the same as the whole driver’s ed “don’t brake and swerve at the same time.” You have a static bank of traction with which to brake, accelerate, and/or turn the vehicle. Overdraw your traction bank and you lose control – which on a bike means “hello, pavement.”

    You brake before you tip in (in street riding; in racing the riders are often on the brakes almost right up to the apex, but their brakes and tires are ridiculously good), look where you want to go, lean the bike over, and as soon as you hit the apex of the turn, roll on the throttle.

    At speed and with traction, a motorcycle is a surprisingly stable system. I’ve seen many a YouTube video in which a rider falls completely off of the bike only to have the bike straighten up and cruise on down the track until it hits a bump or slows down enough to fall over. It’s when you unexpectedly lose traction…water, oil, gravel or sand on the road, for example…that bad things happen quickly. Or of course when some jerk turns left right in front of you, saying “I didn’t see him!!”

    A moderator on one of my motorcycle forums used to use the signature, “Motorcycling is a constant physics lesson. Beware the pop quizzes.”

  3. I asked Calvin if he ever dragged his knee when he did MotoCross (which of course, no, they’re about sticking their foot out to get around turns on the dirt tracks), and he was all, “No, but I ended up in a tree after some whoops, once.”

    Right, motocross and flat-trackers stick their inside foot out. Flat-trackers usually wear a metal boot, in fact. Kenny Roberts started sticking his knee out because he was used to the whole foot thing from his flat-track days.

    I’ve never said hello to a tree before, ouch.

  4. There was some French guy (whose name I can’t remember right now) who had kind of a funny position where he really hung off with his upper body — and he dragged his *elbow*! I have a magazine with photos of him cornering, and the scuff marks on his leathers elbow later. (You can see in the photo above that Rossi’s inside elbow isn’t really that far from the ground.)

    As far as leaning that far, the big thing is just how much traction the tires have. Remember that these guys are riding on tires that are totally optimized for short-term traction — the race tires are totally shot after one race (around 100 miles).

    I’ve heard of a few guys dragging their elbows also – Supposedly AMA racer Aaron Yates used to do it with some regularity at the Mid-Ohio course?

    And good point about the race tires. You should see a set of race tires after the race, with the used rubber pilled up in little balls around the edges. It’s strange.

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